This document provides an overview of fundamental concepts in physics. It discusses physics as the study of fundamental principles of the universe. The objectives of physics are to find fundamental laws that govern natural phenomena and use them to develop mathematical theories that can predict experimental results. Theories are developed based on experiments and make predictions that are tested. Fundamental quantities like length, mass and time form the basis for defining other physical quantities. Standard systems of measurement like the SI system are discussed. The document also covers dimensional analysis, scientific notation, and significant figures which are important concepts in physics measurements.

1. Chapter 1
Physics and Measurements
Yasser Assran
Dimension
1
13/10/2015

2. Physics
Fundamental Science
 Concerned with the fundamental principles of
the Universe
 Foundation of other physical sciences
 Has simplicity of fundamental concepts
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3. Objectives of Physics
To find the limited number of fundamental laws that
govern natural phenomena
To use these laws to develop theories that can predict the
results of future experiments
Express the laws in the language of mathematics
 Mathematics provides the bridge between theory and
experiment.
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4. Theories and Experiments
 The goal of physics is to develop theories based
on experiments
 A theory is a “guess,” expressed mathematically,
about how a system works
 The theory makes predictions about how a system
should work
 Experiments check the theories’ predictions
 Every theory is a work in progress
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5. Fundamental Quantities and Their
Dimension
 Length [L]
 Mass [M]
 Time [T]
 other physical quantities can be constructed from
these three
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6. Units
 To communicate the result of a measurement for a
quantity, a unit must be defined
 Defining units allows everyone to relate to the
same fundamental amount
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7. Systems of Measurement
 Standardized systems
 agreed upon by some authority, usually a
governmental body
 SI -- Systéme International
 agreed to in 1960 by an international committee
 main system used in this text
 also called mks for the first letters in the units
of the fundamental quantities
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8. Systems of Measurements, cont
 cgs – Gaussian system
 named for the first letters of the units it uses for
fundamental quantities
 US Customary
 everyday units
 often uses weight, in pounds, instead of mass as a
fundamental quantity
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9. Length
 Units
 SI – meter, m
 cgs – centimeter, cm
 US Customary – foot, ft
 Defined in terms of a meter – the distance traveled
by light in a vacuum during a given time
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10. Mass
Units
 SI – kilogram, kg
 cgs – gram, g
 USC – slug, slug
 Defined in terms of kilogram, based on a specific
cylinder kept at the International Bureau of
Weights and Measures
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11. Time
 Units
 seconds, s in all three systems
 Defined in terms of the oscillation of radiation from a
cesium atom
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12. The Seven Base SI Units
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13. Prefixes
 Prefixes correspond to powers of 10
 Each prefix has a specific name
 Each prefix has a specific abbreviation
 See next table
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14. STANDARD PREFIXES
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15. Structure of Matter
 Matter is made up of molecules
 the smallest division that is identifiable as a
substance
 Molecules are made up of atoms
 correspond to elements
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16. More structure of matter
 Atoms are made up of
 nucleus, very dense, contains

protons, positively charged, “heavy”

neutrons, no charge, about same mass as
protons
 protons and neutrons are made up of
quarks
 orbited by

electrons, negatively charges, “light”
 fundamental particle, no structure13/10/2015 Dimension 16

17. 13/10/2015 Dimension 17

18. 13/10/2015 Dimension 18

19. 13/10/2015 Dimension 19

20. 13/10/2015 Dimension 20

21. Structure of Matter
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22. Dimensional Analysis
 Technique to check the correctness of an equation.
 Dimensions (length, mass, time, combinations)
can be treated as algebraic quantities.
 add, subtract, multiply, divide
 Both sides of equation must have the same
dimensions
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23. Dimensional Analysis, cont.
 Cannot give numerical factors: this is
its limitation
 Dimensions of some common
quantities are listed in next Table.
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24. Dimensional Analysis, cont.
Dimensions are often denoted with
square brackets.
Length [L]
Mass [M]
Time [T]
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25. 13/10/2015 Dimension 25

26. Dimensional Analysis,
example
 Check the correctness of the next equation in
dimension analysis point of view.
 Left hand side is T
 Right hand side has dimension of
Left hand side = Right hand side
Equation is correct
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t=2π l / g

27. Example
 The viscosity η of a gas depends on the mass, the
effective diameter and the mean speed of the molecules.
Use dimensional analysis to find η as a function of these
variables.
Solution
Assume that
η = k ma
db
vc
,
Where k, a, b, and c are dimensionless constants, m is
the mass, d the diameter and v the mean speed of a
molecule.
from our own knowledge) the dimensions of viscosity are13/10/2015 Dimension 27

28. Example Cont.
[M][L-1
][T-1
].
Thus
[M][L-1
][T-1
] = [Ma
][Lb
][Lc
][T-c
],
so, by inspection,
a = 1, b = -2, c = 1
and hence
η=k m v/d2
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29. Scientific Notation
13/10/2015 Dimension 29
 M x10^n
 M is the coefficient 1<M<10
 10 is the base
 n is the exponent or power of 10.
 A millionth of a second is:
0.000001 sec 1x10-6
1.0E-6 1.0^-6

30. What is a significant figure?
 There are 2 kinds of numbers:
 Exact: the amount of money in your account.
Known with certainty.
 Approximate: weight, height—anything
MEASURED. No measurement is perfect.
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31. Significant Figures
 Rule: All digits are significant starting with the first
non-zero digit on the left.
 Exception to rule: In whole numbers that end in zero,
the zeros at the end are not significant.
 2nd
Exception to rule: If zeros are sandwiched between
non-zero digits, the zeros become significant.
 3rd Exception to rule: If zeros are at the end of a
number that has a decimal, the zeros are significant.
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32. How many sig figs?
 7
 40
 0.5
 0.00003
 7 x 105
 1
 1
 1
 1
 1
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33. How many sig figs here?
 3401
 2100
 2100.0
 5.00
 0.00412
 8,000,050,000
 4
 2
 5
 3
 3
 6
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34. Operations with Significant
Figures
 Rule: When adding or subtracting measured numbers,
the answer can have no more places after the decimal
than the LEAST of the measured numbers.
 Rule: When multiplying or dividing, the result can have
no more significant figures than the least reliable
measurement.
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35. Operations with Significant
Figures
 56.78 cm x 2.45cm = 139.111 cm2
 Round to  139cm2
75.8cm x 9.6cm = ?
 2.45cm + 1.2cm = 3.65cm,
 Round off to = 3.7cm
 7.432cm + 2cm = 9.432 round to  9cm13/10/2015 Dimension 35

36. Solving Problems
 Analyze
 List knowns and unknowns.
 Draw a diagram.
 Devise a plan.
 Write the math equation to be used.
 Calculate
 If needed, rearrange the equation to solve for
the unknown.
 Substitute the knowns with units in the
equation and express the answer with units.
 Evaluate
 Is the answer reasonable?13/10/2015 Dimension 36

37. ThanksTalk’s Link
https://www.dropbox.com/s/pdpyqvxr57w12k6/Dime
0
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